//===---- CodeCompleteConsumer.h - Code Completion Interface ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file defines the CodeCompleteConsumer class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_SEMA_CODECOMPLETECONSUMER_H
#define LLVM_CLANG_SEMA_CODECOMPLETECONSUMER_H

#include "clang/AST/Type.h"
#include "clang/AST/CanonicalType.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Allocator.h"
#include "clang-c/Index.h"
#include <string>

namespace llvm {
  class raw_ostream;
  class Twine;
}

namespace clang {

class Decl;
  
/// \brief Default priority values for code-completion results based
/// on their kind.
enum {
  /// \brief Priority for the next initialization in a constructor initializer
  /// list.
  CCP_NextInitializer = 7,
  /// \brief Priority for an enumeration constant inside a switch whose 
  /// condition is of the enumeration type.
  CCP_EnumInCase = 7,
  /// \brief Priority for a send-to-super completion.
  CCP_SuperCompletion = 20,
  /// \brief Priority for a declaration that is in the local scope.
  CCP_LocalDeclaration = 34,
  /// \brief Priority for a member declaration found from the current
  /// method or member function.
  CCP_MemberDeclaration = 35,
  /// \brief Priority for a language keyword (that isn't any of the other
  /// categories).
  CCP_Keyword = 40,
  /// \brief Priority for a code pattern.
  CCP_CodePattern = 40,
  /// \brief Priority for a non-type declaration.
  CCP_Declaration = 50,
  /// \brief Priority for a type.
  CCP_Type = CCP_Declaration,
  /// \brief Priority for a constant value (e.g., enumerator).
  CCP_Constant = 65,
  /// \brief Priority for a preprocessor macro.
  CCP_Macro = 70,
  /// \brief Priority for a nested-name-specifier.
  CCP_NestedNameSpecifier = 75,
  /// \brief Priority for a result that isn't likely to be what the user wants,
  /// but is included for completeness.
  CCP_Unlikely = 80,
  
  /// \brief Priority for the Objective-C "_cmd" implicit parameter.
  CCP_ObjC_cmd = CCP_Unlikely
};

/// \brief Priority value deltas that are added to code-completion results
/// based on the context of the result.
enum {
  /// \brief The result is in a base class.
  CCD_InBaseClass = 2,
  /// \brief The result is a C++ non-static member function whose qualifiers
  /// exactly match the object type on which the member function can be called.
  CCD_ObjectQualifierMatch = -1,
  /// \brief The selector of the given message exactly matches the selector
  /// of the current method, which might imply that some kind of delegation
  /// is occurring.
  CCD_SelectorMatch = -3,
  
  /// \brief Adjustment to the "bool" type in Objective-C, where the typedef
  /// "BOOL" is preferred.
  CCD_bool_in_ObjC = 1,
  
  /// \brief Adjustment for KVC code pattern priorities when it doesn't look
  /// like the
  CCD_ProbablyNotObjCCollection = 15
};

/// \brief Priority value factors by which we will divide or multiply the
/// priority of a code-completion result.
enum {
  /// \brief Divide by this factor when a code-completion result's type exactly
  /// matches the type we expect.
  CCF_ExactTypeMatch = 4,
  /// \brief Divide by this factor when a code-completion result's type is
  /// similar to the type we expect (e.g., both arithmetic types, both
  /// Objective-C object pointer types).
  CCF_SimilarTypeMatch = 2
};

/// \brief A simplified classification of types used when determining
/// "similar" types for code completion.
enum SimplifiedTypeClass {
  STC_Arithmetic,
  STC_Array,
  STC_Block,
  STC_Function,
  STC_ObjectiveC,
  STC_Other,
  STC_Pointer,
  STC_Record,
  STC_Void
};
  
/// \brief Determine the simplified type class of the given canonical type.
SimplifiedTypeClass getSimplifiedTypeClass(CanQualType T);
  
/// \brief Determine the type that this declaration will have if it is used
/// as a type or in an expression.
QualType getDeclUsageType(ASTContext &C, NamedDecl *ND);
  
/// \brief Determine the priority to be given to a macro code completion result
/// with the given name.
///
/// \param MacroName The name of the macro.
///
/// \param LangOpts Options describing the current language dialect.
///
/// \param PreferredTypeIsPointer Whether the preferred type for the context
/// of this macro is a pointer type.
unsigned getMacroUsagePriority(llvm::StringRef MacroName, 
                               const LangOptions &LangOpts,
                               bool PreferredTypeIsPointer = false);

/// \brief Determine the libclang cursor kind associated with the given
/// declaration.
CXCursorKind getCursorKindForDecl(Decl *D);
  
class FunctionDecl;
class FunctionType;
class FunctionTemplateDecl;
class IdentifierInfo;
class NamedDecl;
class NestedNameSpecifier;
class Sema;

/// \brief The context in which code completion occurred, so that the
/// code-completion consumer can process the results accordingly.
class CodeCompletionContext {
public:
  enum Kind {
    /// \brief An unspecified code-completion context.
    CCC_Other,
    /// \brief An unspecified code-completion context where we should also add
    /// macro completions.
    CCC_OtherWithMacros,
    /// \brief Code completion occurred within a "top-level" completion context,
    /// e.g., at namespace or global scope.
    CCC_TopLevel,
    /// \brief Code completion occurred within an Objective-C interface,
    /// protocol, or category interface.
    CCC_ObjCInterface,
    /// \brief Code completion occurred within an Objective-C implementation
    /// or category implementation.
    CCC_ObjCImplementation,
    /// \brief Code completion occurred within the instance variable list of
    /// an Objective-C interface, implementation, or category implementation.
    CCC_ObjCIvarList,
    /// \brief Code completion occurred within a class, struct, or union.
    CCC_ClassStructUnion,
    /// \brief Code completion occurred where a statement (or declaration) is
    /// expected in a function, method, or block.
    CCC_Statement,
    /// \brief Code completion occurred where an expression is expected.
    CCC_Expression,
    /// \brief Code completion occurred where an Objective-C message receiver
    /// is expected.
    CCC_ObjCMessageReceiver,
    /// \brief Code completion occurred on the right-hand side of a member
    /// access expression.
    ///
    /// The results of this completion are the members of the type being 
    /// accessed. The type itself is available via 
    /// \c CodeCompletionContext::getType().
    CCC_MemberAccess,
    /// \brief Code completion occurred after the "enum" keyword, to indicate
    /// an enumeration name.
    CCC_EnumTag,
    /// \brief Code completion occurred after the "union" keyword, to indicate
    /// a union name.
    CCC_UnionTag,
    /// \brief Code completion occurred after the "struct" or "class" keyword,
    /// to indicate a struct or class name.
    CCC_ClassOrStructTag,
    /// \brief Code completion occurred where a protocol name is expected.
    CCC_ObjCProtocolName,
    /// \brief Code completion occurred where a namespace or namespace alias
    /// is expected.
    CCC_Namespace,
    /// \brief Code completion occurred where a type name is expected.
    CCC_Type,
    /// \brief Code completion occurred where a new name is expected.
    CCC_Name,
    /// \brief Code completion occurred where a new name is expected and a
    /// qualified name is permissible.
    CCC_PotentiallyQualifiedName,
    /// \brief Code completion occurred where an macro is being defined.
    CCC_MacroName,
    /// \brief Code completion occurred where a macro name is expected
    /// (without any arguments, in the case of a function-like macro).
    CCC_MacroNameUse,
    /// \brief Code completion occurred within a preprocessor expression.
    CCC_PreprocessorExpression,
    /// \brief Code completion occurred where a preprocessor directive is 
    /// expected.
    CCC_PreprocessorDirective,
    /// \brief Code completion occurred in a context where natural language is
    /// expected, e.g., a comment or string literal.
    ///
    /// This context usually implies that no completions should be added,
    /// unless they come from an appropriate natural-language dictionary.
    CCC_NaturalLanguage,
    /// \brief Code completion for a selector, as in an @selector expression.
    CCC_SelectorName,
    /// \brief Code completion within a type-qualifier list.
    CCC_TypeQualifiers,
    /// \brief Code completion in a parenthesized expression, which means that
    /// we may also have types here in C and Objective-C (as well as in C++).
    CCC_ParenthesizedExpression,
    /// \brief An unknown context, in which we are recovering from a parsing 
    /// error and don't know which completions we should give.
    CCC_Recovery
  };

private:
  enum Kind Kind;

  /// \brief The type that would prefer to see at this point (e.g., the type
  /// of an initializer or function parameter).
  QualType PreferredType;
  
  /// \brief The type of the base object in a member access expression.
  QualType BaseType;
  
public:
  /// \brief Construct a new code-completion context of the given kind.
  CodeCompletionContext(enum Kind Kind) : Kind(Kind) { }
  
  /// \brief Construct a new code-completion context of the given kind.
  CodeCompletionContext(enum Kind Kind, QualType T) : Kind(Kind) { 
    if (Kind == CCC_MemberAccess)
      BaseType = T;
    else
      PreferredType = T;
  }
  
  /// \brief Retrieve the kind of code-completion context.
  enum Kind getKind() const { return Kind; }
  
  /// \brief Retrieve the type that this expression would prefer to have, e.g.,
  /// if the expression is a variable initializer or a function argument, the
  /// type of the corresponding variable or function parameter.
  QualType getPreferredType() const { return PreferredType; }
  
  /// \brief Retrieve the type of the base object in a member-access 
  /// expression.
  QualType getBaseType() const { return BaseType; }

  /// \brief Determines whether we want C++ constructors as results within this
  /// context.
  bool wantConstructorResults() const;
};


/// \brief A "string" used to describe how code completion can
/// be performed for an entity.
///
/// A code completion string typically shows how a particular entity can be 
/// used. For example, the code completion string for a function would show
/// the syntax to call it, including the parentheses, placeholders for the 
/// arguments, etc.  
class CodeCompletionString {
public:
  /// \brief The different kinds of "chunks" that can occur within a code
  /// completion string.
  enum ChunkKind {
    /// \brief The piece of text that the user is expected to type to
    /// match the code-completion string, typically a keyword or the name of a
    /// declarator or macro.
    CK_TypedText,
    /// \brief A piece of text that should be placed in the buffer, e.g.,
    /// parentheses or a comma in a function call.
    CK_Text,
    /// \brief A code completion string that is entirely optional. For example,
    /// an optional code completion string that describes the default arguments
    /// in a function call.
    CK_Optional,
    /// \brief A string that acts as a placeholder for, e.g., a function 
    /// call argument.
    CK_Placeholder,
    /// \brief A piece of text that describes something about the result but
    /// should not be inserted into the buffer.
    CK_Informative,
    /// \brief A piece of text that describes the type of an entity or, for
    /// functions and methods, the return type.
    CK_ResultType,
    /// \brief A piece of text that describes the parameter that corresponds
    /// to the code-completion location within a function call, message send,
    /// macro invocation, etc.
    CK_CurrentParameter,
    /// \brief A left parenthesis ('(').
    CK_LeftParen,
    /// \brief A right parenthesis (')').
    CK_RightParen,
    /// \brief A left bracket ('[').
    CK_LeftBracket,
    /// \brief A right bracket (']').
    CK_RightBracket,
    /// \brief A left brace ('{').
    CK_LeftBrace,
    /// \brief A right brace ('}').
    CK_RightBrace,
    /// \brief A left angle bracket ('<').
    CK_LeftAngle,
    /// \brief A right angle bracket ('>').
    CK_RightAngle,
    /// \brief A comma separator (',').
    CK_Comma,
    /// \brief A colon (':').
    CK_Colon,
    /// \brief A semicolon (';').
    CK_SemiColon,
    /// \brief An '=' sign.
    CK_Equal,
    /// \brief Horizontal whitespace (' ').
    CK_HorizontalSpace,
    /// \brief Verticle whitespace ('\n' or '\r\n', depending on the
    /// platform).
    CK_VerticalSpace
  };
  
  /// \brief One piece of the code completion string.
  struct Chunk {
    /// \brief The kind of data stored in this piece of the code completion 
    /// string.
    ChunkKind Kind;
    
    union {
      /// \brief The text string associated with a CK_Text, CK_Placeholder,
      /// CK_Informative, or CK_Comma chunk.
      /// The string is owned by the chunk and will be deallocated 
      /// (with delete[]) when the chunk is destroyed.
      const char *Text;
      
      /// \brief The code completion string associated with a CK_Optional chunk.
      /// The optional code completion string is owned by the chunk, and will
      /// be deallocated (with delete) when the chunk is destroyed.
      CodeCompletionString *Optional;
    };
    
    Chunk() : Kind(CK_Text), Text(0) { }
    
    Chunk(ChunkKind Kind, const char *Text = "");
    
    /// \brief Create a new text chunk.
    static Chunk CreateText(const char *Text);

    /// \brief Create a new optional chunk.
    static Chunk CreateOptional(CodeCompletionString *Optional);

    /// \brief Create a new placeholder chunk.
    static Chunk CreatePlaceholder(const char *Placeholder);

    /// \brief Create a new informative chunk.
    static Chunk CreateInformative(const char *Informative);

    /// \brief Create a new result type chunk.
    static Chunk CreateResultType(const char *ResultType);

    /// \brief Create a new current-parameter chunk.
    static Chunk CreateCurrentParameter(const char *CurrentParameter);
  };
  
private:
  /// \brief The number of chunks stored in this string.
  unsigned NumChunks;
  
  /// \brief The priority of this code-completion string.
  unsigned Priority : 30;
  
  /// \brief The availability of this code-completion result.
  unsigned Availability : 2;
  
  CodeCompletionString(const CodeCompletionString &); // DO NOT IMPLEMENT
  CodeCompletionString &operator=(const CodeCompletionString &); // DITTO
  
  CodeCompletionString(const Chunk *Chunks, unsigned NumChunks,
                       unsigned Priority, CXAvailabilityKind Availability);
  ~CodeCompletionString() { }
  
  friend class CodeCompletionBuilder;
  friend class CodeCompletionResult;
  
public:
  typedef const Chunk *iterator;
  iterator begin() const { return reinterpret_cast<const Chunk *>(this + 1); }
  iterator end() const { return begin() + NumChunks; }
  bool empty() const { return NumChunks == 0; }
  unsigned size() const { return NumChunks; }
  
  const Chunk &operator[](unsigned I) const {
    assert(I < size() && "Chunk index out-of-range");
    return begin()[I];
  }
  
  /// \brief Returns the text in the TypedText chunk.
  const char *getTypedText() const;

  /// \brief Retrieve the priority of this code completion result.
  unsigned getPriority() const { return Priority; }
  
  /// \brief Reteirve the availability of this code completion result.
  unsigned getAvailability() const { return Availability; }
  
  /// \brief Retrieve a string representation of the code completion string,
  /// which is mainly useful for debugging.
  std::string getAsString() const;   
};

/// \brief An allocator used specifically for the purpose of code completion.
class CodeCompletionAllocator : public llvm::BumpPtrAllocator { 
public:
  /// \brief Copy the given string into this allocator.
  const char *CopyString(llvm::StringRef String);

  /// \brief Copy the given string into this allocator.
  const char *CopyString(llvm::Twine String);
  
  // \brief Copy the given string into this allocator.
  const char *CopyString(const char *String) {
    return CopyString(llvm::StringRef(String));
  }
  
  /// \brief Copy the given string into this allocator.
  const char *CopyString(const std::string &String) {
    return CopyString(llvm::StringRef(String));
  }
};
  
/// \brief A builder class used to construct new code-completion strings.
class CodeCompletionBuilder {
public:  
  typedef CodeCompletionString::Chunk Chunk;
  
private:
  CodeCompletionAllocator &Allocator;
  unsigned Priority;
  CXAvailabilityKind Availability;
  
  /// \brief The chunks stored in this string.
  llvm::SmallVector<Chunk, 4> Chunks;
  
public:
  CodeCompletionBuilder(CodeCompletionAllocator &Allocator) 
    : Allocator(Allocator), Priority(0), Availability(CXAvailability_Available){
  }
  
  CodeCompletionBuilder(CodeCompletionAllocator &Allocator,
                        unsigned Priority, CXAvailabilityKind Availability) 
    : Allocator(Allocator), Priority(Priority), Availability(Availability) { }

  /// \brief Retrieve the allocator into which the code completion
  /// strings should be allocated.
  CodeCompletionAllocator &getAllocator() const { return Allocator; }
  
  /// \brief Take the resulting completion string. 
  ///
  /// This operation can only be performed once.
  CodeCompletionString *TakeString();
  
  /// \brief Add a new typed-text chunk.
  void AddTypedTextChunk(const char *Text) { 
    Chunks.push_back(Chunk(CodeCompletionString::CK_TypedText, Text));
  }
  
  /// \brief Add a new text chunk.
  void AddTextChunk(const char *Text) { 
    Chunks.push_back(Chunk::CreateText(Text)); 
  }

  /// \brief Add a new optional chunk.
  void AddOptionalChunk(CodeCompletionString *Optional) {
    Chunks.push_back(Chunk::CreateOptional(Optional));
  }
  
  /// \brief Add a new placeholder chunk.
  void AddPlaceholderChunk(const char *Placeholder) {
    Chunks.push_back(Chunk::CreatePlaceholder(Placeholder));
  }
  
  /// \brief Add a new informative chunk.
  void AddInformativeChunk(const char *Text) {
    Chunks.push_back(Chunk::CreateInformative(Text));
  }
  
  /// \brief Add a new result-type chunk.
  void AddResultTypeChunk(const char *ResultType) {
    Chunks.push_back(Chunk::CreateResultType(ResultType));
  }
  
  /// \brief Add a new current-parameter chunk.
  void AddCurrentParameterChunk(const char *CurrentParameter) {
    Chunks.push_back(Chunk::CreateCurrentParameter(CurrentParameter));
  }
  
  /// \brief Add a new chunk.
  void AddChunk(Chunk C) { Chunks.push_back(C); }
};
  
/// \brief Captures a result of code completion.
class CodeCompletionResult {
public:
  /// \brief Describes the kind of result generated.
  enum ResultKind {
    RK_Declaration = 0, //< Refers to a declaration
    RK_Keyword,         //< Refers to a keyword or symbol.
    RK_Macro,           //< Refers to a macro
    RK_Pattern          //< Refers to a precomputed pattern.
  };
    
  /// \brief The kind of result stored here.
  ResultKind Kind;
    
  union {
    /// \brief When Kind == RK_Declaration, the declaration we are referring
    /// to.
    NamedDecl *Declaration;
      
    /// \brief When Kind == RK_Keyword, the string representing the keyword 
    /// or symbol's spelling.
    const char *Keyword;
      
    /// \brief When Kind == RK_Pattern, the code-completion string that
    /// describes the completion text to insert.
    CodeCompletionString *Pattern;
      
    /// \brief When Kind == RK_Macro, the identifier that refers to a macro.
    IdentifierInfo *Macro;
  };

  /// \brief The priority of this particular code-completion result.
  unsigned Priority;

  /// \brief The cursor kind that describes this result.
  CXCursorKind CursorKind;
    
  /// \brief The availability of this result.
  CXAvailabilityKind Availability;
    
  /// \brief Specifies which parameter (of a function, Objective-C method,
  /// macro, etc.) we should start with when formatting the result.
  unsigned StartParameter;
    
  /// \brief Whether this result is hidden by another name.
  bool Hidden : 1;
    
  /// \brief Whether this result was found via lookup into a base class.
  bool QualifierIsInformative : 1;
    
  /// \brief Whether this declaration is the beginning of a 
  /// nested-name-specifier and, therefore, should be followed by '::'.
  bool StartsNestedNameSpecifier : 1;

  /// \brief Whether all parameters (of a function, Objective-C
  /// method, etc.) should be considered "informative".
  bool AllParametersAreInformative : 1;

  /// \brief Whether we're completing a declaration of the given entity,
  /// rather than a use of that entity.
  bool DeclaringEntity : 1;
    
  /// \brief If the result should have a nested-name-specifier, this is it.
  /// When \c QualifierIsInformative, the nested-name-specifier is 
  /// informative rather than required.
  NestedNameSpecifier *Qualifier;
    
  /// \brief Build a result that refers to a declaration.
  CodeCompletionResult(NamedDecl *Declaration, 
                       NestedNameSpecifier *Qualifier = 0,
                       bool QualifierIsInformative = false)
    : Kind(RK_Declaration), Declaration(Declaration), 
      Priority(getPriorityFromDecl(Declaration)), 
      Availability(CXAvailability_Available), StartParameter(0), 
      Hidden(false), QualifierIsInformative(QualifierIsInformative),
      StartsNestedNameSpecifier(false), AllParametersAreInformative(false),
      DeclaringEntity(false), Qualifier(Qualifier) { 
    computeCursorKindAndAvailability();
  }
    
  /// \brief Build a result that refers to a keyword or symbol.
  CodeCompletionResult(const char *Keyword, unsigned Priority = CCP_Keyword)
    : Kind(RK_Keyword), Keyword(Keyword), Priority(Priority), 
      Availability(CXAvailability_Available), 
      StartParameter(0), Hidden(false), QualifierIsInformative(0), 
      StartsNestedNameSpecifier(false), AllParametersAreInformative(false),
      DeclaringEntity(false), Qualifier(0) {
    computeCursorKindAndAvailability();
  }
    
  /// \brief Build a result that refers to a macro.
  CodeCompletionResult(IdentifierInfo *Macro, unsigned Priority = CCP_Macro)
    : Kind(RK_Macro), Macro(Macro), Priority(Priority), 
      Availability(CXAvailability_Available), StartParameter(0), 
      Hidden(false), QualifierIsInformative(0), 
      StartsNestedNameSpecifier(false), AllParametersAreInformative(false),
      DeclaringEntity(false), Qualifier(0) { 
    computeCursorKindAndAvailability();
  }

  /// \brief Build a result that refers to a pattern.
  CodeCompletionResult(CodeCompletionString *Pattern,
                       unsigned Priority = CCP_CodePattern,
                       CXCursorKind CursorKind = CXCursor_NotImplemented,
                   CXAvailabilityKind Availability = CXAvailability_Available)
    : Kind(RK_Pattern), Pattern(Pattern), Priority(Priority), 
      CursorKind(CursorKind), Availability(Availability), StartParameter(0), 
      Hidden(false), QualifierIsInformative(0), 
      StartsNestedNameSpecifier(false), AllParametersAreInformative(false), 
      DeclaringEntity(false), Qualifier(0) 
  { 
  }
    
  /// \brief Retrieve the declaration stored in this result.
  NamedDecl *getDeclaration() const {
    assert(Kind == RK_Declaration && "Not a declaration result");
    return Declaration;
  }
    
  /// \brief Retrieve the keyword stored in this result.
  const char *getKeyword() const {
    assert(Kind == RK_Keyword && "Not a keyword result");
    return Keyword;
  }
    
  /// \brief Create a new code-completion string that describes how to insert
  /// this result into a program.
  ///
  /// \param S The semantic analysis that created the result.
  ///
  /// \param Allocator The allocator that will be used to allocate the
  /// string itself.
  CodeCompletionString *CreateCodeCompletionString(Sema &S,
                                           CodeCompletionAllocator &Allocator);
    
  /// \brief Determine a base priority for the given declaration.
  static unsigned getPriorityFromDecl(NamedDecl *ND);
    
private:
  void computeCursorKindAndAvailability();
};
  
bool operator<(const CodeCompletionResult &X, const CodeCompletionResult &Y);
  
inline bool operator>(const CodeCompletionResult &X, 
                      const CodeCompletionResult &Y) {
  return Y < X;
}
  
inline bool operator<=(const CodeCompletionResult &X, 
                      const CodeCompletionResult &Y) {
  return !(Y < X);
}

inline bool operator>=(const CodeCompletionResult &X, 
                       const CodeCompletionResult &Y) {
  return !(X < Y);
}

  
llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, 
                              const CodeCompletionString &CCS);

/// \brief Abstract interface for a consumer of code-completion 
/// information.
class CodeCompleteConsumer {
protected:
  /// \brief Whether to include macros in the code-completion results.
  bool IncludeMacros;

  /// \brief Whether to include code patterns (such as for loops) within
  /// the completion results.
  bool IncludeCodePatterns;
  
  /// \brief Whether to include global (top-level) declarations and names in
  /// the completion results.
  bool IncludeGlobals;
  
  /// \brief Whether the output format for the code-completion consumer is
  /// binary.
  bool OutputIsBinary;
  
public:
  class OverloadCandidate {
  public:
    /// \brief Describes the type of overload candidate.
    enum CandidateKind {
      /// \brief The candidate is a function declaration.
      CK_Function,
      /// \brief The candidate is a function template.
      CK_FunctionTemplate,
      /// \brief The "candidate" is actually a variable, expression, or block
      /// for which we only have a function prototype.
      CK_FunctionType
    };
    
  private:
    /// \brief The kind of overload candidate.
    CandidateKind Kind;
    
    union {
      /// \brief The function overload candidate, available when 
      /// Kind == CK_Function.
      FunctionDecl *Function;
      
      /// \brief The function template overload candidate, available when
      /// Kind == CK_FunctionTemplate.
      FunctionTemplateDecl *FunctionTemplate;
      
      /// \brief The function type that describes the entity being called,
      /// when Kind == CK_FunctionType.
      const FunctionType *Type;
    };
    
  public:
    OverloadCandidate(FunctionDecl *Function)
      : Kind(CK_Function), Function(Function) { }

    OverloadCandidate(FunctionTemplateDecl *FunctionTemplateDecl)
      : Kind(CK_FunctionTemplate), FunctionTemplate(FunctionTemplateDecl) { }

    OverloadCandidate(const FunctionType *Type)
      : Kind(CK_FunctionType), Type(Type) { }

    /// \brief Determine the kind of overload candidate.
    CandidateKind getKind() const { return Kind; }
    
    /// \brief Retrieve the function overload candidate or the templated 
    /// function declaration for a function template.
    FunctionDecl *getFunction() const;
    
    /// \brief Retrieve the function template overload candidate.
    FunctionTemplateDecl *getFunctionTemplate() const {
      assert(getKind() == CK_FunctionTemplate && "Not a function template");
      return FunctionTemplate;
    }
    
    /// \brief Retrieve the function type of the entity, regardless of how the
    /// function is stored.
    const FunctionType *getFunctionType() const;
    
    /// \brief Create a new code-completion string that describes the function
    /// signature of this overload candidate.
    CodeCompletionString *CreateSignatureString(unsigned CurrentArg, 
                                                Sema &S,
                                      CodeCompletionAllocator &Allocator) const;
  };
  
  CodeCompleteConsumer() : IncludeMacros(false), IncludeCodePatterns(false),
                           IncludeGlobals(true), OutputIsBinary(false) { }
  
  CodeCompleteConsumer(bool IncludeMacros, bool IncludeCodePatterns,
                       bool IncludeGlobals, bool OutputIsBinary)
    : IncludeMacros(IncludeMacros), IncludeCodePatterns(IncludeCodePatterns),
      IncludeGlobals(IncludeGlobals), OutputIsBinary(OutputIsBinary) { }
  
  /// \brief Whether the code-completion consumer wants to see macros.
  bool includeMacros() const { return IncludeMacros; }

  /// \brief Whether the code-completion consumer wants to see code patterns.
  bool includeCodePatterns() const { return IncludeCodePatterns; }
  
  /// \brief Whether to include global (top-level) declaration results.
  bool includeGlobals() const { return IncludeGlobals; }
  
  /// \brief Determine whether the output of this consumer is binary.
  bool isOutputBinary() const { return OutputIsBinary; }
  
  /// \brief Deregisters and destroys this code-completion consumer.
  virtual ~CodeCompleteConsumer();

  /// \name Code-completion callbacks
  //@{
  /// \brief Process the finalized code-completion results.
  virtual void ProcessCodeCompleteResults(Sema &S, 
                                          CodeCompletionContext Context,
                                          CodeCompletionResult *Results,
                                          unsigned NumResults) { }

  /// \param S the semantic-analyzer object for which code-completion is being
  /// done.
  ///
  /// \param CurrentArg the index of the current argument.
  ///
  /// \param Candidates an array of overload candidates.
  ///
  /// \param NumCandidates the number of overload candidates
  virtual void ProcessOverloadCandidates(Sema &S, unsigned CurrentArg,
                                         OverloadCandidate *Candidates,
                                         unsigned NumCandidates) { }
  //@}
  
  /// \brief Retrieve the allocator that will be used to allocate
  /// code completion strings.
  virtual CodeCompletionAllocator &getAllocator() = 0;
};

/// \brief A simple code-completion consumer that prints the results it 
/// receives in a simple format.
class PrintingCodeCompleteConsumer : public CodeCompleteConsumer {
  /// \brief The raw output stream.
  llvm::raw_ostream &OS;
    
  CodeCompletionAllocator Allocator;
  
public:
  /// \brief Create a new printing code-completion consumer that prints its
  /// results to the given raw output stream.
  PrintingCodeCompleteConsumer(bool IncludeMacros, bool IncludeCodePatterns,
                               bool IncludeGlobals,
                               llvm::raw_ostream &OS)
    : CodeCompleteConsumer(IncludeMacros, IncludeCodePatterns, IncludeGlobals,
                           false), OS(OS) {}
  
  /// \brief Prints the finalized code-completion results.
  virtual void ProcessCodeCompleteResults(Sema &S, 
                                          CodeCompletionContext Context,
                                          CodeCompletionResult *Results,
                                          unsigned NumResults);
  
  virtual void ProcessOverloadCandidates(Sema &S, unsigned CurrentArg,
                                         OverloadCandidate *Candidates,
                                         unsigned NumCandidates);  
  
  virtual CodeCompletionAllocator &getAllocator() { return Allocator; }
};
  
} // end namespace clang

#endif // LLVM_CLANG_SEMA_CODECOMPLETECONSUMER_H
